Compositions comprising lignin

ABSTRACT

Compositions comprising lignin and low levels of undesirable impurities, such as compounds containing sulfur, nitrogen, or metals, are disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Application No. 61/581,865,filed Dec. 30, 2011, the entire disclosure of which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention generally relates to compositions comprisinglignin containing maximum levels of undesirable impurities, such ascompounds containing sulfur, nitrogen, or metals.

BACKGROUND OF THE INVENTION

There are a number of processes for converting lignocellulosic biomassinto liquid streams of various sugars. Certain preferred processes arebased on supercritical water (SCW) or hot compressed water (HCW)technology, which offer several advantages including high throughputs,use of mixed feedstocks, separation of sugars, and avoidance ofconcentrated acids, microbial cultures, and enzymes. Processes using hotcompressed water may have two distinct operations: pre-treatment andcellulose hydrolysis. The pre-treatment process hydrolyzes thehemicellulose component of the lignocellulosic biomass and cellulosehydrolysis (CH) process hydrolyzes the cellulose fibers. The resultantfive carbon (C5) and six carbon (C6) sugar streams are recoveredseparately. The remaining solids, which consist mostly of lignin, arepreferably recovered, such as through filtration, and may be used as afuel to provide thermal energy to the process itself or for otherprocesses. Lignin has the combustion heat of 26.6 KJ/g, and holdshighest energy among all natural polymeric compounds that containcarbon, hydrogen and oxygen. In energy, lignin is equivalent to ethanol,which also contains carbon, hydrogen and oxygen, and has the combustionheat of 30 KJ/g. However, for a given volume, lignin's combustion heatis approximately 1.5 times as much as that of ethanol, because oflignin's higher density.http://www.altenergymag.com/emagazine/2009/06/lignin-as-alternative-renewable-fuel/1384).Thus, lignin serves as a useful renewable energy source.

Lignocellulosic biomass contains cellulose, hemicellulose, and lignin,along with minor amounts of proteins, lipids (fats, waxes, and oils) andminerals. About two thirds of the dry mass of cellulosic materials ispresent as cellulose and hemicellulose with lignin making up the bulk ofthe remaining dry mass. Lignin is a cross-linked racemic macromoleculewith a molecular masse in excess of 10,000 Daltons. It is relativelyhydrophobic and aromatic in nature. The degree of polymerization innature is difficult to measure, since it is fragmented during extractionand the molecule consists of various types of substructures that appearto repeat in a haphazard manner. Different types of lignin have beendescribed depending on the means of isolation. “Lignin and itsProperties: Glossary of Lignin Nomenclature,” Dialogue/NewslettersVolume 9, Number 1, Lignin Institute, July 2001.

There are three monolignol monomers, methoxylated to various degrees:p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. K.Freudenberg & A. C. Nash (eds) (1968). Constitution and Biosynthesis ofLignin. Berlin: Springer-Verlag. These lignols are incorporated intolignin in the form of the phenylpropanoids p-hydroxyphenyl (H), guaiacyl(G), and syringal (S), respectively. W. Boerjan, J. Ralph, M. Baucher(June 2003). “Lignin bios”. Ann. Rev. Plant Biol. 54 (1): 519-549.Gymnosperms have a lignin that consists almost entirely of G with smallquantities of H. That of dicotyledonous angiosperms is more often thannot a mixture of G and S (with very little H), and monocotyledonouslignin is a mixture of all three. Id. Many grasses have mostly G, whilesome palms have mainly S. All lignins contain small amounts ofincomplete or modified monolignols, and other monomers are prominent innon-woody plants. J. Ralph, et al. (2001). “Elucidation of newstructures in lignins of CAD- and COMT-deficient plants by NMR.”Phytochem. 57 (6): 993-1003.

Impurities may be introduced into lignin via processing of thelignocellulosic biomass. Since lignin compositions may be used as a fuelin the SCW or HCW process or other processes, they preferably have a lowlevel of contaminants or impurities that contribute to health,environmental, and safety concerns. For example, it is highly desirableto have no or only a low level of compounds containing sulfur in thelignin composition, as the presence of sulfur may contribute to SOxemissions, when the lignin is combusted. In other applications, lowlevels of sulfur may also be desirable if lignin is chemically convertedthrough a catalytic process to a downstream product or a derivative. Lowlevels of sulfur within the final product may also be desirable fromproduct acceptance criteria, or low levels of sulfur may help preventpremature catalyst deactivation for such chemical conversions.

Accordingly, the invention is directed to lignin compositions having lowlevels of impurities, as well as other important ends.

SUMMARY OF THE INVENTION

In one embodiment, the invention is directed to compositions,comprising:

lignin; and

less than about 2000 mg in total per kg of said lignin of elements;

wherein said elements are Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K,Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn.

In some embodiments, the compositions further comprise less than about700 mg of calcium per kg of said lignin. In other embodiments, thecompositions further comprise less than about 525 mg of iron per kg ofsaid lignin. In yet other embodiments, the compositions further compriseless than about 150 mg of sulfur per kg of said lignin. In someembodiments, the compositions further comprise less than about 20 g ofash per kg of said lignin. In other embodiments, the compositionscomprise less than about 2000 mg of nitrogen per kg of said lignin. Inyet other embodiments, the compositions further comprise a weight ratioof the total mass of hydrogen and nitrogen to carbon of less than about0.110.

In other embodiments, the invention is directed to compositions,comprising:

lignin;

less than about 700 mg of calcium per kg of said lignin;

less than about 525 mg of iron per kg of said lignin; and

less than about 150 mg of sulfur per kg of said lignin.

In some embodiments, the compositions comprise less than about 2000 mgin total per kg of said lignin of elements; wherein said elements areAl, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P,Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn.

In yet other embodiments, the invention is directed to compositions,comprising:

lignin; and

less than about 700 mg of calcium per kg of said lignin.

In some embodiments, the compositions comprise less than about 2000 mgin total per kg of said lignin of elements; wherein said elements areAl, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P,Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn.

In yet further embodiments, the invention is directed to compositions,comprising:

lignin; and

less than about 525 mg of iron per kg of said lignin.

In some embodiments, the compositions comprise less than about 2000 mgin total per kg of said lignin of elements; wherein said elements areAl, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P,Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn.

In yet another embodiment, the invention is directed to compositions,comprising:

lignin; and

less than about 150 mg of sulfur per kg of said lignin.

In some embodiments, the compositions comprise less than about 2000 mgin total per kg of said lignin of elements; wherein said elements areAl, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P,Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn.

DETAILED DESCRIPTION OF THE INVENTION

As employed above and throughout the disclosure, the following terms,unless otherwise indicated, shall be understood to have the followingmeanings.

As used herein, the singular forms “a,” “an,” and “the” include theplural reference unless the context clearly indicates otherwise.

While the present invention is capable of being embodied in variousforms, the description below of several embodiments is made with theunderstanding that the present disclosure is to be considered as anexemplification of the invention, and is not intended to limit theinvention to the specific embodiments illustrated. Headings are providedfor convenience only and are not to be construed to limit the inventionin any manner. Embodiments illustrated under any heading may be combinedwith embodiments illustrated under any other heading.

The use of numerical values in the various quantitative values specifiedin this application, unless expressly indicated otherwise, are stated asapproximations as though the minimum and maximum values within thestated ranges were both preceded by the word “about.” In this manner,slight variations from a stated value can be used to achievesubstantially the same results as the stated value. Also, the disclosureof ranges is intended as a continuous range including every valuebetween the minimum and maximum values recited as well as any rangesthat can be formed by such values. Also disclosed herein are any and allratios (and ranges of any such ratios) that can be formed by dividing arecited numeric value into any other recited numeric value. Accordingly,the skilled person will appreciate that many such ratios, ranges, andranges of ratios can be unambiguously derived from the numerical valuespresented herein and in all instances such ratios, ranges, and ranges ofratios represent various embodiments of the present invention.

As used herein, the phrase “substantially free” means have no more thanabout 1%, preferably less than about 0.5%, more preferably, less thanabout 0.1%, by weight of a component, based on the total weight of anycomposition containing the component.

A supercritical fluid is a fluid at a temperature above its criticaltemperature and at a pressure above its critical pressure. Asupercritical fluid exists at or above its “critical point,” the pointof highest temperature and pressure at which the liquid and vapor (gas)phases can exist in equilibrium with one another. Above criticalpressure and critical temperature, the distinction between liquid andgas phases disappears. A supercritical fluid possesses approximately thepenetration properties of a gas simultaneously with the solventproperties of a liquid. Accordingly, supercritical fluid extraction hasthe benefit of high penetrability and good solvation.

Reported critical temperatures and pressures include: for pure water, acritical temperature of about 374.2° C., and a critical pressure ofabout 221 bar; for carbon dioxide, a critical temperature of about 31°C. and a critical pressure of about 72.9 atmospheres (about 1072 psig).Near critical water has a temperature at or above about 300° C. andbelow the critical temperature of water (374.2° C.), and a pressure highenough to ensure that all fluid is in the liquid phase. Sub-criticalwater has a temperature of less than about 300° C. and a pressure highenough to ensure that all fluid is in the liquid phase. Sub-criticalwater temperature may be greater than about 250° C. and less than about300° C., and in many instances sub-critical water has a temperaturebetween about 250° C. and about 280° C. The term “hot compressed water”is used interchangeably herein for water that is at or above itscritical state, or defined herein as near-critical or sub-critical, orany other temperature above about 50° C. (preferably, at least about100° C.) but less than subcritical and at pressures such that water isin a liquid state

As used herein, a fluid which is “supercritical” (e.g. supercriticalwater, supercritical CO₂, etc.) indicates a fluid which would besupercritical if present in pure form under a given set of temperatureand pressure conditions. For example, “supercritical water” indicateswater present at a temperature of at least about 374.2° C. and apressure of at least about 221 bar, whether the water is pure water, orpresent as a mixture (e.g. water and ethanol, water and CO₂, etc.).Thus, for example, “a mixture of sub-critical water and supercriticalcarbon dioxide” indicates a mixture of water and carbon dioxide at atemperature and pressure above that of the critical point for carbondioxide but below the critical point for water, regardless of whetherthe supercritical phase contains water and regardless of whether thewater phase contains any carbon dioxide. For example, a mixture ofsub-critical water and supercritical CO₂ may have a temperature of about250° C. to about 280° C. and a pressure of at least about 225 bar.

As used herein, “lignocellulosic biomass or a component part thereof”refers to plant biomass containing cellulose, hemicellulose, and ligninfrom a variety of sources, including, without limitation (1)agricultural residues (including corn stover and sugarcane bagasse), (2)dedicated energy crops, (3) wood residues (including hardwoods,softwoods, sawmill and paper mill discards), and (4) municipal waste,and their constituent parts including without limitation, lignocellulosebiomass itself, lignin, C₆ saccharides (including cellulose, cellobiose,C₆ oligosaccharides, C₆ monosaccharides, C₅ saccharides (includinghemicellulose, C₅ oligosaccharides, and C₅ monosaccharides), andmixtures thereof.

As used herein, “ash” refers to the non-aqueous residue that remainsafter a sample is burned, and consists mostly of metal oxides. Ashcontent may be measured in accordance with ASTM Standard Method No.E1755-01 “Standard Method for the Determination of Ash in Biomass.” Thistest method covers the determination of ash, expressed as the percentageof residue remaining after dry oxidation at 550 to 600° C. All resultsare reported relative to the 105° C. oven dry weight of the sample.” Seealso: http://www.nrel.gov/biomass/pdfs/42622.pdf andhttp://www.astm.orq/Standards/62630/838168 E1755.htm, which are bothincorporated herein by reference in their entirety.

Accordingly, in one embodiment, the invention is directed tocompositions, comprising:

-   -   lignin; and    -   less than about 2000 mg, preferably less than about 1775 mg, in        total per kg of said lignin of elements;    -   wherein said elements are Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu,        Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti,        Tl, V, and Zn.

In other embodiments, the invention is directed to compositions,comprising:

lignin;

less than about 700 mg, preferably less than about 675 mg, of calciumper kg of said lignin;

less than about 525 mg, preferably less than about 505 mg, of iron perkg of said lignin; and

less than about 150 mg, preferably less than about 147 mg, of sulfur perkg of said lignin.

In some embodiments, the compositions comprise:

lignin; and

less than about 700 mg, preferably less than about 675 mg, of calciumper kg of said lignin.

In some embodiments, the compositions comprise:

lignin; and

less than about 525 mg, preferably less than about 505 mg, of iron perkg of said lignin.

In some embodiments, the compositions comprise:

lignin; and

less than about 150 mg, preferably less than about 147 mg, of sulfur perkg of said lignin.

In some embodiments, the compositions comprise less than about 2000 mg,preferably less than 1775 mg, in total per kg of said lignin ofelements; wherein said elements are Al, As, B, Ba, Be, Ca, Cd, Co, Cr,Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl,V, and Zn.

In some embodiments, the compositions further comprise less than about700 mg, preferably less than about 675 mg, of calcium per kg of saidlignin. In other embodiments, the compositions further comprise lessthan about 525 mg of iron per kg of said lignin. In yet otherembodiments, the compositions further comprise less than about 150 mg ofsulfur per kg of said lignin.

In some embodiments, the lignin has a heating value as measured byASTM-D240 and D5865 of at least about 5,000 BTU/lb, preferably at leastabout 7,500 BTU/lb, and more preferably, at least about 8,000 BTU/lb.

In some embodiments, the lignin has an average particle size less thanabout 500 microns. In preferred embodiments, the lignin has an averageunaggregated particle size less than about 100 microns. In otherpreferred embodiments, the lignin has an average unaggregated particlesize less than about 60 microns.

In some embodiments, the lignin has a bulk density of less than about0.35 g/cc, depending upon particle size.

In some embodiments, the lignin is processed from lignocellulosicbiomass optionally using supercritical, subcritical, or near criticalfluid extraction or combinations thereof.

In some embodiments, the composition is substantially free of organicsolvent.

In some embodiments, the lignin is in a powdered form. In otherembodiments, the lignin is in a pelletized form. In yet otherembodiments, the lignin is in a liquid form. In addition, the lignin maybe in combination of these forms.

In some embodiments, is present at a level of at least 30% by weight,based on the total weight of the composition, as measured by pyrolysismolecular beam mass spectrometry.

In some embodiments, the weight ratio of syringyl monolignol to guaiacylmonolignol is about 2.0 to about 3.0, as measured by pyrolysis molecularbeam mass spectrometry.

In some embodiments, the compositions further comprise less than about700 mg, preferably less than about 675 mg, of calcium per kg of saidlignin.

In some embodiments, the compositions further comprise less than about525 mg, preferably less than about 505 mg, of iron per kg of saidlignin.

In some embodiments, the compositions further comprise less than about150 mg, preferably less than about 147 mg, of sulfur per kg of saidlignin.

In some embodiments, the levels of said elements are measured byinductively coupled plasma emission spectroscopy.

In some embodiments, the compositions further comprise less than about20 g of ash per kg of said lignin, preferably less than about 17.5 g ofash per kg of said lignin.

In other embodiments, the compositions comprise less than about 2000 mgof nitrogen per kg of said lignin, preferably less than about 1900 mg ofnitrogen per kg of said lignin. Nitrogen may be measured by thermalconductivity detection after combustion and reduction.

In yet other embodiments, the compositions further comprise a weightratio of the total mass of hydrogen and nitrogen to carbon of less thanabout 0.110, preferably less than about 0.105. Carbon, hydrogen, andnitrogen levels may be measured by thermal conductivity detection aftercombustion and reduction.

In certain other embodiments, the compositions comprising the ligninfurther comprise less than a maximum of any of the elements,individually or in combination, in the table listed below:

Level less than about Element (mg of element/kg of lignin) Al 50 As 16 B3.25 Ba 3.7 Be 0.04 Cd 0.850 Co 1.25 Cr 2.0 Cu 20.0 K 45.0 Li 0.310 Mg22.5 Mn 7.00 Mo 3.00 Na 61.5 Ni 1.50 P 115 Pb 10.00 Sb 9.50 Se 21.0 Si65.0 Sn 11.00 Sr 2.25 Ti 6.00 Tl 21.0 V 0.350 Zn 11.5

In further embodiments, the compositions further comprise less thanabout 0.5% by weight, based on the total weight of said lignin, oforganic solvent, such as alcohols, including water miscible loweraliphatic C₁-C₄ alcohols (e.g., methanol, ethanol, isopropanol,t-butanol). In preferred embodiments, the compositions contain less thanabout 0.1% by weight, based on the total weight of said lignin oforganic solvent. In more preferred embodiments, the compositions containsubstantially no organic solvent.

The compositions of the invention are preferably prepared from biomassby processes employing supercritical, subcritical, and/or near criticalwater, preferably without the addition of acid. The processes mayinclude pretreatment step or steps using supercritical or near criticalwater to separate the C5 sugars (monomers and/or oligomers) fromcellulose and lignin. In the pretreatment step, suitable temperaturesare about 130° C. to about 250° C., suitable pressures are about 4 barsto about 100 bars, and suitable residence times are about 0.5 minutes toabout 5 hours. The processes may also include a cellulose hydrolysisstep or steps using supercritical or near critical water to separate thecellulose (which may processed to form C6 monomeric and/or oligomericsugars) from the lignin. In the hydrolysis step(s), suitabletemperatures are about 250° C. to about 450° C., suitable pressures areabout 40 bars to about 260 bars, and suitable residence times are about0.1 seconds to about 3 minutes.

The compositions of the invention may be prepared in any suitablereactor, including, but not limited to, a tubular reactor, a digester(vertical, horizontal, or inclined), or the like. Suitable digestersinclude the digester system described in U.S. Pat. No. 8,057,639, whichinclude a digester and a steam explosion unit, the entire disclosure ofwhich is incorporated by reference.

The compositions of the invention comprising lignin may be utilized in avariety of applications, including, but not limited to, fuels,tackifiers, phenol formaldehyde resin extenders in the manufacture ofparticle board and plywood, in the manufacture of molding compounds,urethane and epoxy resins, antioxidants, controlled-release agents, flowcontrol agents, cement/concrete mixing, plasterboard production, oildrilling, general dispersion, tanning leather, road covering, vanillinproduction, dimethyl sulfide and dimethyl sulfoxide production, phenolsubstitute in phenolic resins incorporation into polyolefin blends,aromatic (phenol) monomers, additional miscellaneous monomers, carbonfibers, metal sequestration in solutions, basis of gel formation,polyurethane copolymer—as a renewable filler/extender, and the like.

The present invention is further defined in the following Examples, inwhich all parts and percentages are by weight, unless otherwise stated.It should be understood that these examples, while indicating preferredembodiments of the invention, are given by way of illustration only andare not to be construed as limiting in any manner. From the abovediscussion and these examples, one skilled in the art can ascertain theessential characteristics of this invention, and without departing fromthe spirit and scope thereof, can make various changes and modificationsof the invention to adapt it to various usages and conditions.

EXAMPLES Example 1 Preparation of Lignin Compositions

Lignin compositions of the invention were prepared using supercritical,subcritical, and near critical water extraction in a two stage process.Particulate lignocellulosic biomass consisting of mixed hardwood chipsof 140 mesh or less was mixed with water to form a slurry (about 20% byweight solids). The slurry was heated to a temperature of about 170-245°C. and then feed into a pretreatment reactor for about 1-120 minutesunder sufficient pressure to keep the water in the liquid phase. Thepretreated slurry was then cooled to a temperature less than about 100°C. under little (less than about 10 bar) or no pressure. The pretreatedsolids were then separated from the liquid stream using a filter press.Alternatively, the solids may be separated using a centrifugal filterpressor. The pretreated solids were then mixed with water to form aslurry and the slurry was heated to a temperature of about 150-250° C.The slurry was then subjected to supercritical water at about 374-600°C. in a hydrolysis reactor for about 0.05-10 seconds under a pressure ofabout 230-300 bar. After exiting the hydrolysis reactor, the hydrolyzedslurry was quenched with water and then flashed to about ambienttemperature and pressure to remove water. The lignin solids were thenseparated from the liquid stream using a centrifugal decanter and airdried.

Example 2 Analysis of Lignin Compositions Using Inductively CoupledPlasma

The dried compositions containing the lignin of Example 1 were analyzedusing inductively coupled plasma emission spectroscopy. The results areshown in the table below:

Sample A Duplicate Sample B Duplicate Sample C Duplicate ReportedReported Reported Reported Reported Reported ICP Conc. Conc. Conc. Conc.Conc. Conc. element (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg)Average Al 45.5 47.8 39.1 37.5 43.6 40.4 42.3 As < 12.6 < 14.6 < 12.1 <12.5 < 13.6 < 15.6 13.5 B 3.22 0.777 2.88 1.66 0.603 < 0.605 1.6 Ba 3.343.62 2.99 2.99 3.02 2.77 3.1 Be < 0.0300 < 0.0349 < 0.0288 < 0.0299 <0.0326 < 0.0374 0.0 Ca 618 671 551 535 594 545 585.7 Cd < 0.667 < 0.777< 0.640 < 0.665 < 0.724 < 0.830 0.7 Co < 0.972 < 1.13 < 0.933 < 0.969 <1.05 < 1.21 1.0 Cr 1.56 1.94 1.60 1.66 1.33 1.38 1.6 Cu 5.89 8.80 7.267.87 6.64 19.0 9.2 Fe 465 501 313 298 351 320 374.6 K 39.1 40.4 23.731.1 33.1 44.1 35.3 Li < 0.245 < 0.285 < 0.235 < 0.244 < 0.266 < 0.3040.3 Mg 21.9 22.1 18.8 19.0 18.6 19.8 20.0 Mn 5.89 6.47 5.02 4.99 4.344.01 5.1 Mo < 2.34 < 2.72 < 2.25 < 2.33 < 2.54 < 2.91 2.5 Na 58.7 52.054.6 40.7 50.6 61.0 52.9 Ni < 1.16 < 1.35 < 1.12 < 1.16 < 1.26 < 1.451.3 P < 89.9 < 105 < 86.2 < 89.6 < 97.5 < 112 96.6 Pb < 7.95 < 9.25 <7.63 < 7.92 < 8.63 < 9.89 8.5 S 105 132 146 128 128 103 123.6 Sb < 7.46< 8.68 < 7.16 < 7.43 < 8.09 < 9.28 8.0 Se < 16.5 < 19.2 < 15.9 < 16.5 <18.0 < 20.6 17.8 Si 54.9 63.9 42.1 57.2 67.6 64.5 58.4 Sn 9.23 9.19 7.047.65 10.9 10.1 9.0 Sr 2.11 2.20 1.81 1.77 1.93 1.80 1.9 Ti 3.56 5.572.77 5.87 3.26 3.46 4.1 Tl < 16.7 < 19.5 < 16.1 < 16.7 < 18.2 < 20.818.0 V < 0.260 < 0.303 < 0.250 0.332 < 0.282 < 0.324 0.3 Zn 9.79 11.09.28 9.86 7.48 6.37 9.0 Total 1610.3 1762.1 1378.7 1347.2 1496.6 1441.41506.0 Elements

Example 3 Analysis of Lignin for Carbon, Hydrogen, and Nitrogen

Dried compositions containing lignin were analyzed to determine thelevels of ash, carbon, hydrogen, and nitrogen by thermal conductivitydetection after combustion and reduction. The results are shown in thetable below:

Element/Material Sample 1 Sample 2 C 56.76% 57.09% H 5.46% 5.66% N 0.18%0.19% Ash 1.1% 1.1% Ratio of N + H:C 0.099 0.102

Example 4 Lignin Characterization

The NREL method for lignin (acid hydrolysis followed by gravimetricprotocol in accordance with standard NREL procedures found athttp://www. nrel.qov/biomass/pdfs/42618.pdf and pyrolysis molecular beammass spectrometry (py-MBMS) were used to quantify the level of lignin inthe solids, using lignin from hardwood as a standard. The results areshown in the table below:

Lignin Lignin Syringyl/Guaiacyl Weight % Weight % Weight Ratio from NRELfrom py-MBMS from py-MBMS Sample Method Method Method Hardwood 28 23.32.6 standard Pretreated 40-44 21.6 2.4 solids Solid residue >50 33.3 2.5after supercritical hydrolysis

When ranges are used herein for physical properties, such as molecularweight, or chemical properties, such as chemical formulae, allcombinations, and subcombinations of ranges specific embodiments thereinare intended to be included.

The disclosures of each patent, patent application, and publicationcited or described in this document are hereby incorporated herein byreference, in their entirety.

Those skilled in the art will appreciate that numerous changes andmodifications can be made to the preferred embodiments of the inventionand that such changes and modifications can be made without departingfrom the spirit of the invention. It is, therefore, intended that theappended claims cover all such equivalent variations as fall within thetrue spirit and scope of the invention.

What is claimed is:
 1. A composition, comprising: lignin; and less thanabout 2000 mg in total per kg of said lignin of elements; wherein saidelements are Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn,Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn; whereinsaid composition is produced by a process comprising: providing amixture comprising lignocellulosic biomass and water; heating saidmixture to a first temperature of about 130° C. to about 250° C. andmaintaining said first temperature for a period of about 0.5 min toabout 5 hours, thereby producing a solids fraction and a liquidfraction; and subjecting said solids fraction to a supercritical ornear-critical fluid under a pressure of about 40 bar to about 300 bar;wherein said supercritical or near-critical fluid comprises water;wherein said supercritical or near-critical fluid is at a temperature ofabout 374° C. to about 600° C.; wherein said subjecting step elevatessaid solids fraction to a second temperature of about 250° C. to about450° C.; and wherein said solids fraction is maintained at said secondtemperature for a period of about 0.05 sec to about 10 sec.
 2. Acomposition of claim 1, wherein said lignin has an average particle sizeless than about 500 microns.
 3. A composition of claim 1, wherein saidlignin has a bulk density of less than about 0.35 g/cc.
 4. A compositionof claim 1, wherein said lignin is in a powdered form.
 5. A compositionof claim 1, wherein said lignin is in a pelletized form.
 6. Acomposition of claim 1, further comprising: less than about 700 mg ofcalcium per kg of said lignin.
 7. A composition of claim 1, furthercomprising: less than about 525 mg of iron per kg of said lignin.
 8. Acomposition of claim 1, further comprising: less than about 150 mg ofsulfur per kg of said lignin.
 9. A composition of claim 1, furthercomprising: less than about 20 g of ash per kg of said lignin.
 10. Acomposition of claim 1, further comprising: less than about 2000 mg ofnitrogen per kg of said lignin.
 11. A composition of claim 1, furthercomprising: a weight ratio of the total mass of hydrogen and nitrogen tocarbon of less than about 0.110.
 12. A composition of claim 1, whereinsaid lignin is present at a level of at least 30% by weight, based onthe total weight of the composition, as measured by pyrolysis molecularbeam mass spectrometry.
 13. A composition of claim 1, wherein the weightratio of syringyl monolignol to guaiacyl monolignol is about 2.0 toabout 3.0, as measured by pyrolysis molecular beam mass spectrometry.14. A composition of claim 1, wherein said heating is performed at apressure of about 4 bar to about 100 bar.
 15. A composition of claim 1,wherein said heating is performed for a period of about 1 min to about120 min.
 16. A composition of claim 1, wherein said supercritical ornear-critical fluid is under a pressure of about 230 bar to about 300bar.
 17. A composition of claim 1, wherein said supercritical ornear-critical fluid is under a pressure of about 40 bar to about 260bar.
 18. A composition of claim 1, wherein said composition issubstantially free of organic solvent.
 19. A composition, comprising:lignin; less than about 700 mg of calcium per kg of said lignin; lessthan about 525 mg of iron per kg of said lignin; and less than about 150mg of sulfur per kg of said lignin; wherein said composition is producedby a process comprising: providing a mixture comprising lignocellulosicbiomass and water; heating said mixture to a first temperature of about130° C. to about 250° C. and maintaining said first temperature for aperiod of about 0.5 min to about 5 hours, thereby producing a solidsfraction and a liquid fraction; and subjecting said solids fraction to asupercritical or near-critical fluid under a pressure of about 40 bar toabout 300 bar; wherein said supercritical or near-critical fluidcomprises water; wherein said supercritical or near-critical fluid is ata temperature of about 374° C. to about 600° C.; wherein said subjectingstep elevates said solids fraction to a second temperature of about 250°C. to about 450° C.; and wherein said solids fraction is maintained atsaid second temperature for a period of about 0.05 sec to about 10 sec.20. A composition of claim 19, further comprising: less than about 2000mg in total per kg of said lignin of elements; wherein said elements areAl, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P,Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn.
 21. A composition,comprising: lignin; and less than about 525 mg of iron per kg of saidlignin; wherein said composition is produced by a process comprising:providing a mixture comprising lignocellulosic biomass and water;heating said mixture to a first temperature of about 130° C. to about250° C. and maintaining said first temperature for a period of about 0.5min to about 5 hours, thereby producing a solids fraction and a liquidfraction; and subjecting said solids fraction to a supercritical ornear-critical fluid under a pressure of about 40 bar to about 300 bar;wherein said supercritical or near-critical fluid comprises water;wherein said supercritical or near-critical fluid is at a temperature ofabout 374° C. to about 600° C.; wherein said subjecting step elevatessaid solids fraction to a second temperature of about 250° C. to about450° C.; and wherein said solids fraction is maintained at said secondtemperature for a period of about 0.05 sec to about 10 sec.
 22. Acomposition of claim 21, further comprising: less than about 700 mg ofcalcium per kg of said lignin.
 23. A composition of claim 21, furthercomprising: less than about 2000 mg in total per kg of said lignin ofelements; wherein said elements are Al, As, B, Ba, Be, Ca, Cd, Co, Cr,Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl,V, and Zn.
 24. A composition, comprising: lignin; and less than about150 mg of sulfur per kg of said lignin; wherein said composition isproduced by a process comprising: providing a mixture comprisinglignocellulosic biomass and water; heating said mixture to a firsttemperature of about 130° C. to about 250° C. and maintaining said firsttemperature for a period of about 0.5 min to about 5 hours, therebyproducing a solids fraction and a liquid fraction; and subjecting saidsolids fraction to a supercritical or near-critical fluid under apressure of about 40 bar to about 300 bar; wherein said supercritical ornear-critical fluid comprises water; wherein said supercritical ornear-critical fluid is at a temperature of about 374° C. to about 600°C.; wherein said subjecting step elevates said solids fraction to asecond temperature of about 250° C. to about 450° C.; and wherein saidsolids fraction is maintained at said second temperature for a period ofabout 0.05 sec to about 10 sec.
 25. A composition of claim 24, furthercomprising: less than about 2000 mg in total per kg of said lignin ofelements; wherein said elements are Al, As, B, Ba, Be, Ca, Cd, Co, Cr,Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl,V, and Zn.
 26. A composition of claim 24, further comprising: less thanabout 700 mg of calcium per kg of said lignin.
 27. A composition ofclaim 24, further comprising: less than about 525 mg of iron per kg ofsaid lignin.